Equity Equity (Details) (USD $)	3 Months Ended						9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated net income	$ 83,671,000	$ 115,518,000	$ 129,660,000	$ 134,337,000	$ 130,343,000	$ 164,610,000	$ 328,849,000	$ 429,290,000
Other Comprehensive Income (Loss), Net of Tax:
Change in net unrealized (loss) gain on investments, net of tax of nil	(8,700,000)	(1,500,000)	4,400,000	8,700,000	(1,300,000)	(400,000)	(5,800,000)	7,000,000
Change in foreign currency translation adjustment, net of tax of nil	(7,500,000)	2,600,000	6,600,000	6,300,000	(4,800,000)	(2,700,000)	1,700,000	(1,200,000)
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss), unrealized holding gain (loss) on securities arising during period, tax	0	0	0	0	0	0	0	0
Other comprehensive income (loss), foreign currency translation adjustment, tax	0	0	0	0	0	0	0	0
Total other comprehensive income (loss), net of tax	(16,200,000)			15,000,000			(4,100,000)	5,800,000
Consolidated comprehensive income	67,500,000			149,300,000			324,700,000	435,100,000
Adjust for comprehensive loss (income) attributable to noncontrolling interest	0			206,000			100,000	(1,100,000)
Comprehensive income attributable to Juniper Networks	$ 67,500,000			$ 149,500,000			$ 324,800,000	$ 434,000,000